Server Error in '/' Application.

Question

When i run ASP.net Application.

i got error 

Server Error in '/' Application.

Configuration Error

Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive.

Source Error:

Line 8:  <configuration> Line 9:      <system.web> Line 10:         <compilation debug="true" targetFramework="4.0" /> Line 11:     </system.web> Line 12: 

Source File: web.config Line: 10